And let's turn now to the latest volley in the ongoing tariff war. American politicians have vowed to fight new Chinese tariffs on U.S. made cars and SUVs. Michigan Radio's Tracy Samilton has more.

TRACY SAMILTON, BYLINE: In 2010, the U.S. won a Chinese tire-dumping complaint before the World Trade Organization. Then China complained about U.S. poultry dumping. The U.S. said China subsidizes solar panels. Now the fight's over cars. Republican Congressman Kevin Brady of Texas heads a trade subcommittee.

REPRESENTATIVE KEVIN BRADY: They are in effect creating cases out of thin air to try to retaliate against our industries. Unfortunately in this case it's one of our key industries, American auto.

SAMILTON: The new tariffs of up to 20 percent won't devastate American car companies. Ford and GM build almost all their cars for the Chinese market in China and Chrysler exports only a few thousand cars to China. Alan Deardorff is with the Ford School of Public Policy. He takes the long view of the tariff disputes.

ALAN DEARDORFF: These things working their way through the system I think is much better than working outside the system, which is what used to happen before we had the WTO.

SAMILTON: Deardorff says what American politicians are really upset about is China's currency manipulation. That does hurt U.S. companies. The WTO doesn't regulate currency disputes - but it may in the future. Deardorff says that could make these tariff fights with China less frequent. For NPR News, I'm Tracy Samilton in Ann Arbor. Transcript provided by NPR, Copyright NPR.